Security Beeping Issue - Blaupunkt Stereo

Hi there,

I took the Blaupunkt PF1a stereo out of my car (to use a beach speaker system), and wired it to a 12V battery (using the Permanent Voltage connection, rather than the "Code 12V" connection, does this make a difference?)

The Stereo turns on and after entering the radio code it plays music, however there is a constant periodic beeping (every 2 secs) which appears to be some sort of security feature perhaps? This means it is currently pretty much useless, would be really grateful for any advice/knowledge on the issue!

My thoughts:
- No aerial in the back could be the issue, took out aerial connection from car and connected it again... no change.
- Speakers could be the issue, changed speakers, beeping still there.